This section illustrates useful background information without admission of any technique described herein representative of the state of the art.
Biometric non-invasive information is used more and more in today's user devices. Biometric information may provide information on a change in a physiological state of a user's body, even in real-time, based on various biometric signals collected from the body and providing an appropriate information to the user, thereby allowing the user to improved control and awareness.
One example of such biometric information is a heart rate (HR) that is a cardiovascular index that is most prominently observed when people train or exercise. The HR can be measured using various methods. Usually, the HR is measured by counting the number of pulses per unit time using an electrocardiogram signal or a photoplethysmography (PPG) signal. The HR is the number of heartbeats per minute and is expressed in beats per minute (BPM).
Various training techniques may be developed for effective self-control learning using biometric information technique in which a user's HR is measured and reported to the user and an appropriate signal is provided to the user when the user's HR reaches a predetermined target value.
However, pedometers and heart rate monitors can give only an estimate of the user's current physiological condition and even for that they require that the user has given his personal aerobic and anaerobic limits to the user device processing the information. Very often exercises are based on the idea of a constant heart rate during the physical exercise. A constant heart rate makes predicting the future, and the point where the user reaches a certain exhaustion level, impossible from the heart rate. For example, if the physical exercise is such that in the beginning user heart rate is 130, in the end of the exercise still being 130, wherein the user is in the beginning in good shape and in the end really tired, it is clear that a heart rate alone is not sufficient to make predictions about the physical shape of the user. Thus, there is a need for an improved method and apparatus to more accurately estimating of the user physiological condition and improving the user assistance for physical exercises.